Materials that have a low surface energy, such as, for example, polyolefin polymers, have hydrophobic surfaces. The hydrophobic properties of such materials are not desirable in some applications and methods for hydrophilizing low surface energy substrates, including treatment with surfactants and/or high energy treatment, are known. Each of these methods has significant limitations. Surfactant treatments tend to wash off when a treated substrate is exposed to water and the charges imparted to the surface of a treated substrate by high energy treatment tend, particularly in the case of a thermoplastic polymer substrate, to dissipate. The hydrophilic properties of such surfactant treated substrates and high energy treated substrates thus tend to exhibit limited durability. Furthermore, the surfactants that are rinsed off of a treated substrate by exposure to water alter the properties of the water, such as lowering the surface tension, which may also be undesirable.
Hydrophilized polyolefin fabrics are used in some products, including disposable absorbent articles, such as diapers, adult incontinence products, wipes, and feminine hygiene products, wherein a hydrophilic surface is desirable, but the durability of the hydrophilic properties of such surface is limited, due to the limitations of available hydrophilization techniques.
Accordingly, there is a need for more durably hydrophilizing low surface energy substrates.